There is a need for a Hybrid Electric vehicle conversion kit that can replace the components of an existing hydrocarbon fuel powered mechanical drive vehicle, wherein the components of the Hybrid Electric system are designed to fit within the space and weight limitations of the engine compartment of the existing vehicle. There is a need for a Hybrid electric vehicle conversion kit for existing vehicles that is designed with primary focus on ease of conversion, optimization of power generation and use, and automatic control of the hybrid electric drive train in a converted vehicle. This need is particularly intense in some developing countries, whose economies are insufficient to support sales of new Hybrid vehicles, except to the very wealthy. In such developing countries there exist thousands of inexpensive hydrocarbon fuel powered mechanical drive vehicles, which, if converted to Hybrid electric drive by means of a relatively inexpensive conversion kit, could not only reduce the dependence on hydrocarbon fuels and related carbon emissions, but also could be a source of backup electrical power for homes in areas where loss of domestic electric power may occur from time to time.
Moreover there is a need that is applicable to both hybrid conversions and new hybrid vehicles to maximize the efficiency of the electric drive system. Specifically, the maximum power of the drive motor to achieve the desired performance (acceleration) is considerably greater than the average power required (during steady driving). For general use, the maximum power is at least twice that of the worst case steady driving. If the drive motor is sized to the maximum power for acceleration performance, then it operates less efficiently when operating at steady driving conditions and will weigh more than what is required for steady driving conditions. Conversely, if the drive motor is sized to steady driving, the acceleration performance will be unacceptable. The problem then is, within the size and weight constraints, and the need for maximum efficiency, how does one provide an electric motor drive that is maximally efficient at steady state driving conditions while still delivering the desired acceleration performance.
By way of further explanation, in a hybrid vehicle there is a need for, at a minimum, an electric machine for generating power for charging the batteries. This electric machine, commonly referred to as the generator, is generally smaller and more efficient than the hydrocarbon fuel powered engine of the standard vehicle. A second electric machine, the drive motor, is dedicated to the task of driving the wheels (one or more motors may be used for this purpose) but is also used for braking where energy is put back into the batteries using the drive motor as a temporary generator that slows the car while generating power. Specific to conversions, and the goal of maximizing efficiency, there is a need to reduce the weight of the conversion components to a minimum. While this is a consideration in the design of a new hybrid vehicle, it does not have the degree of constraint that one faces in a conversion scenario. The need is therefore that one must keep the total weight of the drive components the same, or ideally less than, the conventional hydrocarbon fuel powered mechanical drive of the original vehicle. In a new vehicle, the design team has the flexibility of adjusting placement and sizing of items and the enclosing vehicle body as needed. A conversion kit's components however, must fit in the available space. Additionally, there is another problem in that hybrid vehicles need some means of powering auxiliary equipment, such as air conditioning, efficiently even when the engine is not operating. Accordingly, the problem then is, within the size and weight constraints, and the need for maximum efficiency, how is a conversion kit designed to have both a highly efficient drive motor and a generator appropriate for hybrid vehicle operations? And in addition, how are the various components controlled to insure this maximum efficiency is realized?